In one method of treating tumors or lesions in solid organs such as the kidney or the liver, a surgical device such as a radio frequency (RF) ablation probe is placed into the tumor and the tumor cells are destroyed using RF energy. Placement of the ablation probe is accomplished using an imaging system, such as ultrasound imaging. An ultrasound imaging system generates a two-dimensional (2D) image, effectively allowing the doctor or surgeon to view the tissue within the image plane of the ultrasound probe. If the ultrasound probe is positioned such that the axis of the ablation and ultrasound probes are co-aligned, the surgeon can observe the placement of the ablation probe in the tissue on the ultrasound image. However, physical limitations frequently prevent inline placement of the ablation and ultrasound probes. If a tumor is large, more than one placement of the ablation probe may be required to address the tumor volume. In cases where the tumor is larger than can be ablated with one application of RF energy, the ablation probe is repositioned as many times as needed and RF energy is applied at each placement of the ablation probe. For multiple ablation probe applications, the doctor is required to mentally process the 2D ultrasound image to create a plan for ablation probe placement and then to execute the plan. Ten to fifteen minutes may pass between placements of the ablation probe. Placement of the ablation probe outside of the image plane of the ultrasound probe adds to the mental challenge of three-dimensional (3D) planning and makes the procedure difficult. Leaving unablated tumor can result in tumor reoccurrence.
Treatment of the tumor is further complicated by the motion of living tissue. The tumor volume and shape will not change within the time frame of the procedure and may not change in days or even longer; however, motions such as breathing and procedural manipulation will continually alter the location of the tumor within the body. Ablation targeting must be performed on a static image. Due to the changes in the tumor location caused by respiration and the like, a plan generated using a static image cannot be used to determine the trajectory of the surgical device from a fixed targeting position to the target tissue.
There is a need for a method and a device for assisting surgeons in positioning ablation probes and other surgical devices to treat tissue within the body. There is also a need for a method for assisting surgeons in visualizing and planning the insertion of surgical devices. There is a further need for a method of compensating for tumor motion due to patient respiration to increase accuracy in placement of surgical devices and improve treatment of tumors.